Factory or field “target” pieces of membrane can be used to extend the life of EPDM membranes.

/Portals/1/images/OnlineImages/0210/B_0210_RN_Diienes.jpg

Since neither polyethylene nor polypropylene has double-bonds sites available for vulcanization, a small amount of a selected diene is added during EPDM production.

/Portals/1/images/OnlineImages/0210/B_0210_RN_EedgeDetail.jpg

The flexibility of EPDM permits the membrane to be bent 90 degrees at roof edges, with the edge metal installed on top of the membrane.

EPDM, Sustainability, and the Environment

/Portals/1/images/OnlineImages/0210/B_0210_RN_EPDM_FactorySealant.jpg

Factory-installed seam tape reduces VOCs in the field.

/Portals/1/images/OnlineImages/0210/B_0210_RN_SulfurLinks.jpg

Sulfur acts to form a three-dimensional network.

/Portals/1/images/OnlineImages/0210/B_0210_RN_Witcheshat.jpg

Witches’ hats are far more durable than pitch-pockets.

/Portals/1/images/OnlineImages/0210/B_0210_RN_StretchedRubber.jpg

When an elastomer is stretched, it behaves elastically, but recovers when the stress is removed.

What material can support a vehicle going 120 mph through a steaming desert and still be flexible at -45 degrees C. (-49 degrees F.)? For roofing applications, materials must also have a high degree of weatherability – especially resistance to water, pollutants, UV rays, and impact and general traffic resistance.

Materials that meet these requirements are called elastomers. ASTM D-1079 defines an elastomer as“a macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weak stress and subsequent release of that stress.”

EPDM has advantages over other elastomers in that its weathering resistance is extraordinary and its raw materials are highly cost effective. Presently, EPDM dominates the elastomeric roofing market, outselling all other materials combined. Among the single-ply roofing systems, EPDM offers building owners the roofing industry’s longest average service life, with more than 40 years of field performance, representing more than 20 billion square feet installed.

Because EPDM polymer doesn’t contain halogens within the polymer chain and isn’t inherently fire resistant, fire ratings can be achieved through two different avenues: the addition of an external fire retardant or via ballasted roof systems that obviate the need for membrane fire resistance. (Rocks don’t burn!)

While compounding of rubber is very complex, the following comments on ingredients may be useful:

The EPDM polymer itself (provides the waterproofing and elastic properties)

For roofing applications, two ingredients deserve further comment. One is the absolute need for carbon black to maximize the physical properties of the EPDM compound. If other fillers could match the performance of black rubber, we would see automobile tires in colors other than black. The carbon black is an excellent UV screening agent and reinforcing substance.

This explains why EPDM is generally furnished as a black material even though it’s not as reflective as light-colored membranes. However, it’s been documented that ballasted roof systems meet the intent of cool roofing design through the thermal inertia provided by the ballast, plus adequate thermal insulation in the system. Some manufacturers provide a white-on-black EPDM sheet. As the white side of the sheet weathers away, the exposed black rubber continues to protect the building. Reflective coatings have also been successful in elevating black EPDM’s reflectivity to meet ENERGY STAR requirements. At the higher levels of thermal insulation now prescribed by ASHRAE 90.1, there’s little difference in energy demand between black and white roofs except in the hotter climates, such as the desert southwest.

The extending oil and high filler concentrations also make EPDM vulnerable to attacks by oils, greases, etc. In a sense, an optimum amount of oil and filler have already been added to the EPDM sheets, and the sheet will accept more oil if it’s present on the roof. EPDM manufacturers offer alternative membranes for those sections of a roof where such exposure occurs.

Hail and Traffic Resistance
When combined with cover boards, such as gypsum board, EPDM membranes can resist impact from 2-inch diameter hailstones or greater. Use of thicker membranes (e.g. 90 mil or roof walkways, or both) will improve durability for heavily trafficked areas.

LEEDEPDM has proven to be extremely durable and maintainable. Warranties have recently been increased to 30 years in many cases; with proper maintenance, life can be extended even longer. Single-ply membranes are thinner than BUR and modified bituminous membranes (45 to 90 mils compared to one-quarter inch or more) so, at the ultimate end of life, there is less volume headed to the landfills. The ballast is recyclable, whereas roofing gravel is embedded in asphalt and can’t be reused (except with great difficulty). From a transportation point of view, ballast and pavers can be produced locally while shipping of large EPDM rolls from the few U.S. factories is not overly burdensome. There has been some success in recycling the rubber membranes, with more than 5 million square feet of membrane recycled in the past 3 years. So far, recyclers will only accept un-adhered membrane – the adhesives and attached insulation facers are too difficult to process.

Elastomeric membranes can’t be heat welded to form watertight seams. Several generations of ways to achieve durable seams include volatile cleaner/primers, solvent-based adhesives (first based upon neoprene, then butyl rubber), and solvent-free butyl tapes. Some of the sheets are also free of talc or have side-lap tape factory-applied to reduce field cleaning. An additional benefit is that the tape is at a prescribed thickness, not subject to the variability of field application by brush or sponge.

Durable AccessoriesFlashings are the most vulnerable part of any roof system. Prefabricated witches’ hats are as durable as the roof membrane, whereas experience with bituminous pitch-pockets indicates that they must be frequently serviced to remain watertight. Roof edge details take advantage of the flexibility of the rubber membrane by carrying the membrane down the fascia at the building edge, so any water that gets under the metal edging is deflected down outside the building itself. Bituminous membranes can’t effectively be bent into a 90-degree angle.

Sustainability and MaintainabilityMany years can be added to an EPDM membrane by placing “target” pieces of fresh membrane at “tee-joints,” inside and outside corners of flashings, curbs, etc. Such retrofitting may qualify the membrane for an extended warranty.

Attachment OptionsEPDM membranes can be loose-laid and ballasted or, depending upon the substrate, fully adhered or mechanically fastened. Membranes can be non-reinforced, internally reinforced, or fleece-backed.

Xcel Energy’s Data Center Efficiency program can help data centers and large-scale IT operations improve reliability and energy efficiency.

Visit our website today to learn about the design flexibility of a Morton building and the endless possibilities of partnering with our designBUILD team.

Wood construction is both cost and energy efficient. Check out Morton Buildings and our designBUILD team online today to discover all the benefits of post-frame construction.

When choosing a metal-clad building for your next construction project, consider Morton Buildings, Inc., and their designBUILD team, we’ll make your dream a reality.

The BUILDINGS brand serves commercial building owners and facilities management professionals for commercial real estate. BUILDINGS brand offers its audience of commercial building owners and facilities management professionals information on the development, construction, modernization, management and operations of commercial buildings as well as the products and services needed to support such commercial buildings and facilities management. With the information we offer, we help facilities management professionals make smarter decisions for commercial buildings.

BUILDINGS delivers relevant and timely information that equips commercial building owners and facilities management professionals with the knowledge and support they need to solve critical issues; energy management, lowering operating costs, new products for commercial buildings, security, and much more.

In addition to content, BUILDINGS features a comprehensive list of products and services and is your link to the companies that provide these valuable facilities management and commercial buildings resources.

You also have the opportunity to maintain your commercial buildings certifications with BUILDINGS. Continuing Education Units are available with approved content from BOMI.